Conceptually, phonetic “distance” is an attempt to quantify the acoustic dissimilarity between phonetic elements, such as phonemes or words. The phonetic distance between similar sounding phonetic elements is less than the phonetic distance between disparate sounding phonetic elements.
Phonetic distance matrices have been compiled listing the phonetic distance between each pair of phonetic elements within a phonetic element set. For instance, the set can include all the phonemes used in a given spoken language, such as English. The phonetic distance matrix is used as a tool in a variety of applications. For example, the phonetic distance matrix can be used to evaluate the grammar of a speech recognition engine. Grammar paths can be selected with sufficient acoustic separation to minimize recognition errors during subsequent operation of the speech recognition engine.
Currently, phonetic distance is estimated based on knowledge of the physiological mechanisms underlying human pronunciation. Conventionally, the phonetic distances thus estimated are rated on a 0-10 scale.